The Molecular Analysis of Genome Instability Core will perform cytological assays to detect chromosome rearrangements, and assays to detect resection of double-strand breaks (DSBs) for program project participants. The Core Directors will consult with the program project investigators in the development of new procedures within our areas of expertise. By centralizing services under the leadership of two experts in chromosome cytology and DNA end resection, the Core will enhance the productivity of the program project members and promote synergy among the projects by providing access to critical methodologies and reagents. To accomplish these goals. Core B will pursue the following specofoc aims: Specific Aim 1: To provide services to analyze DNA end resection by direct physical methods. Specific Aim 2: To perform molecular cytogenetic assays to characterize chromosomal changes in cells derived from in vitro and in vivo experimental models.